A typical automotive air conditioning system comprises a compressor in the engine compartment for compressing refrigerant and delivering the compressed refrigerant to a condenser. The compressed refrigerant is expanded in the condenser, causing to the condenser to be chilled. Air is blown through the chilled condenser, which cools the air, and into the passenger compartment to cool the vehicle. The expanded refrigerant is then returned to the compressor where it is again compressed and the cycle repeats.
The refrigerant loop usually is coupled to the compressor through a compressor manifold having an inlet port communicating with the low pressure side or "low side" of the compressor and an outlet port communicating with the high pressure side or "high side" of the compressor. High pressure compressed refrigerant is delivered to the condenser through a hose coupled to the high pressure port and expanded refrigerant is delivered back to the compressor for recompression through a hose coupled to the low pressure port. In general, the pressure of the refrigerant on the high side can be many times the pressure of the refrigerant on the low side. It is therefore common when the engine of a vehicle is shut off that the pressure differential between the high side and low side of the compressor self equalizes. When this occurs, compressed refrigerant in the hose connected to the high side of the compressor rushes back through the reed valves and cylinder of the compressor and into hoses coupled to the low side until the pressure is equalized. The rush of refrigerant in such an equalization sometimes is heard as an audible hiss after the engine is shut off.
Compressor failure can occur for a number of reasons. One common circumstance in which failure can occur is when debris such as a small sliver of metal from a reed valve, a shard of plastic or metal from a compressor piston ring, or dirt becomes entrained in the refrigerant and circulates through the compressor. Such debris can cause gradual deterioration of compressor components or, in some cases, can result in sudden catastrophic failure. When this occurs, the compressor must be replaced. One problem often associated with replacement of a defective compressor results from the aforementioned equalizing reflux of refrigerant back into the hose coupled to the low side of the compressor during operation of the old compressor. Specifically, debris entrained in the refrigerant becomes lodged in the low side hose and is not always removed by a refrigerant flush. Accordingly, when the new compressor is installed and operated, this debris again becomes entrained within the refrigerant and destroys the new compressor in the same way as the old. In some cases, a number of compressors have been installed on a vehicle only to be destroyed in turn by debris trapped in the system and entrained in the refrigerant. A need therefore exists for a method and apparatus of preventing debris entrained in the refrigerant of an automotive air conditioning system from circulating through a newly installed compressor. It is to the provision of such a method and apparatus that the present invention is primarily directed.